Long tube headers causing knock...?

[Neptune]

Hi All,

Not sure if this is the appropriate forum....

Just fitted 1-7/8" long tubes to my LS2 (E40). I'm now seeing knock at the top end and even when blipping the throttle when stationary.

I was anticipating the lower back pressure if anything to need more timing. What are the usual tweaks that are required with this change?

Hopefully refitting the wideband shortly to change the ratios.

Any help much appreciated, got a long road trip later this week, and would like to bottom out any running issues before if possible.
Thanks

[TAQuickness]

you might check first that the headers are not making contact with the body and all all the fasteners are secure.

[mr.prick]

are you lean when you get KR?

[cmitchell17]

I would think that the headers would cause in increase in airflow in some parts of the rpm range that would need a decrease in timing becuase their is more cyl. pressure so it needs less timing to burn.

But then ive heard that people add timing with the headers becuase headers make it knock less. I did not notice any airflow change with my headers.

I thought my enigne might have been knocking at low rpms high load(like when the torque converter is locked going up a hill) but then I realized its just becuase of the headers. You can hear the noise of the exhuast more with steel headers instead of the stock cast iron pieces. So that might have something to do with it.

[Neptune]

Thanks for the suggestions guys.
I haven't hooked up the widebands yet, but these should show any lean conditions. I'm thinking it may be some false knock somewhere as even the stock tune runnning stock components was picking up knock in strange places.

I was mainly just checking there wasn't any standard changed that have to be made when using replacement headers.

Cheers